The pro-government troops deployed heavy armour supplied by their backers in the assault on Al-Anad base, some 60 kilometres (35 miles) north of Aden, military sources said. “The battle to retake Al-Anad base has begun,” a military source told AFP.

Hundreds of troops and militia equipped with tanks and armoured vehicles supplied by the coalition deployed around the base before Monday’s attack, their commander Fadhl Hassan said. Another source said Saudi-led warplanes were providing air cover for the loyalist forces, who launched the offensive from a mountainous region west of Al-Anad. The airbase, in the southern province of Lahj, housed US troops overseeing a drone war against Al-Qaeda in the Arabian Peninsula (AQAP) until shortly before Iran-backed Huthi rebels overran it in March. The insurgent advance, which took them all the way into the port city of Aden, forced President Abedrabbo Mansour Hadi and his internationally recognised government into exile in Saudi Arabia.

But Aden has now been recaptured and Hadi loyalists are in full control there.

Hundreds of Gulf Arab troops from the coalition entered Aden on Sunday, using tanks and other armour “to help secure” it, a military source told AFP.

The Saudi-owned Al-Hayat newspaper said 1,500 troops, most of them from the United Arab Emirates, had reached Aden. The UAE is a member of the coalition which has carried out more than four months of air strikes targeting the rebels and their allies.

Retaking Al-Anad would help bolster security in Aden, whose liberation Hadi’s government announced in mid-July. It would also open the way to loyalist forces to push further north against the Huthis, who have enjoyed strong support on the ground from fighters close to former president Ali Abdullah Saleh.

An officer taking part in the offensive told AFP the troops had reached the western entrance of Al-Anad by mid-afternoon on Monday.

Fierce fighting was under way, added the officer who asked not to be identified.

The airport reopened on July 22, allowing planes to land with relief supplies from Saudi Arabia, the United Arab Emirates and Qatar.

The United Nations says the war has killed nearly 4,000 people, half of them civilians, while 80 percent of the 21-million population of the impoverished Arabian Peninsula nation needs aid and protection.

The Horn of Africa nation of Djibouti across the Gulf of Aden appealed on Monday for aid after a new influx of refugees from the Yemen conflict.

Almost 10,000 Yemenis - many of them wounded - have arrived in the small state since late March, according to UN refugee agency the UNHCR.

Despite losing Aden, the rebels in Yemen remain in control of the capital Sanaa, which they overran last September, and large swathes of the rest of the country.

Late Sunday, rebel chief Abdulmalik al-Huthi said a political settlement was “still possible” with the exiled government, after the failure of UN-brokered peace talks in Geneva in June.

“We would welcome any (mediation) effort by a neutral party - Arab or international,” he said in a speech broadcast by the rebels’ Al-Masira television station. He also downplayed Aden’s recapture, saying the loyalist advance “will collapse”.